The proposed study is the initial part of a long-term investigation of the neuronal, neurochemical, and synaptic organization of the lateral and basolateral nucleus (L-BL) of the rat amygdala. The major objectives of this proposal are to 1) characterize the cell types that contain somatostatin, CCK, VIP, enkephalin, and GABA; 2) describe the fine structure of different cell classes including the types of terminals that contact their perikarya; 3) determine the relative number of each cell type in each subdivision of L-BL; 4) examine the topographical organization of neurons that project to different brain areas; 5) determine the cell type(s) involved in these projections; 6) estimate the percentage of local circuit neurons in each subdivision; and 7) examine the peptide cytochemistry of neurons projecting to different brain areas. The techniques used to accomplish these aims include the Golgi technique, immunocytochemistry, retrograde axonal transport methods, combined immunocytochemical-HRP axonal transport technique, and electron microscopy. Analysis of cell types will involve a correlation of the morphology of different classes of Golgi-impregnated neurons with neurons stained by other techniques. Various statistical techniques will be used to facilitate correlations between different techniques. The light microscopic portion of the proposed study will elucidate basic aspects of the structural, hodological, and cytochemical organization of L-BL. The electron microscopic investigation initiates a long-term ultrastructural analysis of these nuclei. Future studies in this laboratory will combine Golgi, immunocytochemical, retrograde axoal transport and axonal degeneration techniques with electron microscopy to further clarify the neuronal, cytochemical, and synaptic organization of the lateral and basolateral nuclei. This information, when correlated with electrophysiological and pharmacological data, may ultimately suggest novel ways to alleviate disorders such as hyperaggressive behavior and temporal lobe epilepsy by pharmacologically manipulating the activity of the amygdala.